1. Field of the Invention
The invention relates in general to the field of automated control of work equipment and, in particular, to a multiple-source system for determining the position and orientation of various components of a work machine operating on the grounds of a surface mine.
2. Description of the Related Art
Work machines play an integral part in mining operations and perform a variety of functions. They may excavate and transport ore, stabilize roads and slopes, and provide support functions. Most work machines, such as excavators, shovels, and backhoes, require human operators and move constantly. Their operation is time consuming and labor intensive because of the need for skilled drivers and a large crew to direct the work. For example, if a particular area of a mine needs to be excavated, the area is surveyed and marked before the machine operator can begin to remove the ore. During the process, the operator constantly updates the work machine's position and orientation to remove the ore efficiently. In addition, the work may only occur at certain times during the day to ensure the safety of the operator and the survey crew, especially if the mining conditions are not ideal.
Because of safety and efficiency concerns during mining, there has been much effort to develop automated systems of varying degrees, to control work machines. For example, a fully An automated machine can operate nonstop in a variety of conditions, without putting a human operator in danger. In addition, an automated system may eliminate the need for survey crews by identifying dig locations and automatically updating topographical changes for future work planning. In order for the automated system to be effective, it must account for the position and orientation of the work machine at all times. Various equipment-positioning systems have used a number of triangulation tools such as lasers, radio, microwave, radar, and satellite-based navigational systems, including the United States Global Positioning System (GPS) and the Russian Global Orbiting Navigational Satellite System (GLONASS) and other service components of the general Global Navigation Satellite System (GNSS). These services are generally referred to as “GPS”.
Because fore-aft pitch and side-side roll can affect position and orientation values, some systems have utilized additional devices, such as inclinometers, rate gyros, magnetometers and accelerometers, to assist with equipment positioning.
U.S. Pat. No. 5,438,771 to Sahm et al. uses a single GPS unit to determine the location and orientation of a work machine with a rotatable car body. The system calls for GPS measurements at a known distance from the rotation axis and collects three coordinate positions as the car body rotates around a fixed undercarriage. The system then calculates the orientation plane of the car body and the position of the axis of rotation using the three sets of coordinates. With the calculated data and the known geometry of the work machine, the system can determine the position and orientation of critical machine components.
One problem of the system is that it can only be used with machines with a rotatable car body. In addition, the system can only calculate the orientation plane while the car body is rotating and the undercarriage is not moving. Therefore, if a machine moves to a new location, the system cannot unambiguously calculate the orientation until the undercarriage is motionless and the car body rotates. What is preferred is a system that can continuously track all types of work machines.
U.S. Pat. No. 6,191,732 to Carlson et al. comes close to describing a total picture of the work machine under all conditions by using a single GPS unit with additional devices to determine the position, pitch, roll, and orientation. The system obtains spatial coordinates from the GPS unit and uses inclinometers to measure the pitch and roll. To determine orientation, the system uses a magnetometer and a rate gyroscope to provide the current heading and the angular rate. The system needs an initial value, which the magnetometer usually provides, to use the rate gyro to calculate orientation. Thus, the Carlson approach determines orientation utilizing two position points, but it also relies on the initial orientation provided by the magnetometer. The rate gyro provides valid data, but magnetometers are unsuitable for mining operations due to electromagnetic interference from heavy equipment and mining deposits. Therefore, the system cannot determine an accurate orientation measurement during mining operations.
U.S. Pat. No. 6,191,733 to Dizchavez describes a system that can continuously track all types of work machines utilizing two high precision three-dimensional (3-D) GPS units. The GPS units periodically measure spatial coordinates with respect to a chosen reference. After obtaining two sets of measurements, the system calculates a plane equation fitting the two sets of data and determines the orientation, pitch, and roll of the work machine. With the calculated data and the known geometry of the work machine, the system can determine the position and orientation of critical machine components. One drawback of the system is that it requires valid GPS data from two sources. Thus, if GPS data are not available or unreliable and the work machine moves, the system cannot unambiguously determine the position and orientation until GPS data become available and the machine moves again. What would be preferred is a system that can function with a single 3-D 3-dimensional GPS unit and can compensate for GPS dropouts.
For the foregoing reasons, there is still a need for an improved method of determining location and orientation of a work machine during mining operations. This invention utilizes a novel combination of positioning components and data filtering to achieve these objectives.